Filtering element and new method for its manufacture



Feb. 3, 1942. s. A. RUBISSOW 2,271,662

I I FILTERING ELEMENT AND NEW METHOD FOR ITS MANUFACTURE Filed Jan. 17, 1939 2 Shegts-Sheet 1 Fig.1. Fig.3.

I INVENTOR.

Feb. 3, 1942. G. A. RUBISSOW 2,271,662

I FILTERING ELEMENT AND NEW METHQD FOR ITS MANUFACTURE Filed Jan. 17-, 1939 2 Sheets-Sheet 2 Famed at. 3, w i 2,271,662

' of making new FE or converting the old FE into new FEphavingthe above-mentioned features.

' UNITED-STATES [PATENT OFFICE FILTERING ELEMENT AND NEW METHOD FOR ITS MANUFACTURE George Alexis Rubissow, New York, N. Y. Application January 17, 1939, Serial- No. 251,362 6 Claims. (Cl. 21o 1s9) This invention consists of a new method for I n+ 1=the number of transversal wires per inch the manufacture of filtering elements made from (measured lineally) metal or metal'alloys or .other suitable solids in m'=the numbe of meshes (D) D inch aform of-filtering gauzes, filteringscreens or the tween two of each of the longitudin l like. The so-'-obtained filtering elements will fil- 5 Wi es eas e ll y trate the smallest impurities, and furthermore n=the number-0f meshes (3) per inch bemay have the exact size of the filtering meshes tween two of each of the transversal controllable to any desired size, however small. I wires (measurediineally).

To facilitate the description of this invention H=the smallest diameter of the impurities Y the following abbreviations will ,be employed: to befiltrated. Hmust alw y be la e Filtering element FE"; this will means a filthan D; H D. trating screen, gauze, net or the like made from which e w ll 8 fl 'e- Se wires, and when employingthe word wir "'t i ity co-emcient which varies from .1 will .mean wire, strips or the like in any form (one) when D=H, to any reasonable and made from any suitable material such as 15 sm ll am un G ner lly S=0H or metal, metal alloys; and when employing the 15 S e y i e l word metaP' this will mean any suitable mateofiering absolute security fo fl a insrial as described above. I C=the co-emclent of the lineal thermic-ex-i It is well known that modern industry repension-0f the metalquires filtering elements capable of filtrating the 'q t mp ratu in C n i a under smallest impurities having a maximum diameter which the FE w h used, and l the of about 0.00002" (of an inch) or even less. Stich room temperature of the workshop.

- where this method is applied.

filtering elements are extremely difiicultto obl T ;,=the amount in degrees of the temperatain. They may be provided with certain very thick flltrating blocks from compressed leather, I We i C de e ceeding the T,, screens, chemicals, cloths, earth; etc., but such Whieh the Wires of them are h'" filtrating blocks are. not easy to use as they remuted hefme 'h Bv t pplication of pressure P,,.

quire high pressures and offer the risk of irregu- P=mechanical pressure in pounds per square larities and many other inconveniences.

' The present invention provides a new kind'of inch, t0 which the wires of the FE are FE made from metal wires wherein the spaces submitted without assistance 9 the (the mesh between the wires) are of the smallest: l the materialdesirable dimensions, which FE are very easy tow= h 9 Pressure applied ml the handle and may be used as usual for any kind wires-when they have been previlusly of filter having one or more filtering elements in disc form, screen or circular 'form, etc.

These FE's will be able to filter any kind of grees centigrade higher than the T, provided that the press surfaces of the press apparatus also have a temperaliquids and gases of any nature even if the imt f a mximatel kT o more Duritiesto be eliminated are minute and ex- 40 A T y r I v ceedmgly a K=is an experimental co-eiiicient substantial- This invention consists of a manufacturing a 1y approaching 1 (one) process which provides cheap and easy means firhe further objectsand novgliieatures of this 5 invention will appear more'fully from the fol- In FE the following abbreviations will be emm connection with the accompan drawings ployed? Y i which are however, made only for purposes of D=maximum of the filtering space measschematical illustration and are not intended ured perpendicularly between tw mm 'as a definition of the limit of the invention.

gitudinal wires of the FE. D is the Figure lis a top plan view of one embodiment maximum measure of the mesh-in the. r of a part of a filtering element, wherein 5| are most disadvantageous place. longitudinal wires and 52 are transversal wires,

heated to the temperature of T" delowin'gdetailed description, and in certain cases m+1=the number of longitudinal wires per It may be remarked that the meshes between inch (measured lineally) .55 the longitudinal wires may be so chosen that their Figure 3 is a sectional view of the filtering ele- I ment shown in Figure 1, wherein the wires are of hexagonal form, also abnormally enlargened.

one parallel to another at pre-determined mesh-- distances, the accuracy or which is controlled by Figures 4, 5, 6, and 7 represent a cross-sectional view of a filtering element in which the filtering element i mounted.

Figures 8, 9, 10, and 11 represent a top plan view of a part of a filtering element.

Figure 12 represents-a cross-sectional view of Figure 11. l

Figure 13 represents atop "plan view of a fil tering element enclosed in a rigid frame.

Figure 14 represents a top plan view of a filtering element in the form of a spiral, made from one wire.

Figure 15 is ure 14.

Figure 16 is a top plan view of a filtering element made from two parallel laid wires in a a cross-sectional view of Figspiral form.

Figure 17 is a cross-sectional view of Figure 16.

Figure 18 is atop plan view of a filtering element composed of an elliptical core surrounded by a parallel wire.

of the wires to be employed is a constantknown figure, the quantity of the required meshes per one inch and their D is known, therefore, according to the than of the variation when putting all such wires arallel one to another on a plate, and this so that they will fit into a suitable predetermined gabarit, then the wires will lay one parallel to another and will fit in such a foreseen gabarit measurement; as by way of a first'example they will fit in one inch, or for a second example in 1.2"; or for-a third example in .095 of an inch; then we will obtain three types of difierent FE's each of which will always have the same 11:. number of meshes, but will have different D spaces of meshes, i. e.-

First example D1'=1/m Second example D1=1.2/m Third example D:=0.95/m

direction may be welded to the FE on one or both of the surfaces and may, by this means, reinforce the element itself.

Figure 19 is a cross-sectional view of Figure Figure 20 is a schematical cross-sectional view of a plate and of a filtering element.

Figure 21 is a cross-sectional view of a filtering element placed between two surfaces.

Figure 22 is another cross-sectional view of a filtering element.

Figures 23 and 24' are schematical cross-sectional views of an apparatus for making filtering elements.

All these drawings are to be interpreted schematically, and have been made on'a very large scale (with the exception of Figures, 23 and 24) for illustrative purposes.

The first aspect of this invention consists of portionate to the amount of the degree of the temperature applied to such metals.

For this third aspect special FE should used, composed of longitudinal wires made from any desirable solid material, while the transversal 'wire's should be made from a metal which does mechanical application of pressure P of the FE's wires, which pressure P may be applied perpendicularly, or substantially on any other angle to the FE and when applied, create a deformation of the cross-section of the wires, so that D becomes smaller, due to the cross-sections of the wires becoming wider.

The practical application of this method is very easy-the FE are passed under any kind of suitarrangements-water cylinder with outlet security valve. arrangement and so forth. For-exam ple, FE made from copper wire which we can find on the market which has for instance D1=0.005 will be converted into D: having 0.006. This may easily be done if the pressure-P which is applied can press the wires so that D1 becomes The secondaspect of this invention consists in the composing of the FE by placing the wires when D=0 o (zero), with FE in such. state" (D=zero) thisFEisthen submitted to'athird not expand when heated on T,,+T,, centigrade; the number of m+1 of the longitudinal wires should be sufiicientlygreater than 12-!- 1, the

number of transversal wires. If desired, the transversal wires may be entirely eliminated and replaced by weldingof the longitudinal wires as it will be described further on in this specificaion. 1 This third aspect has three operations-the first one is the heatingof the FEs wires on the T, centigrade higher than 'I,. Once the FEs wires have been so heated to the temperature of T,,, then the same FE still having the temperature of T; degrees higher than T,, is then submitted to a second operation consisting of the application of press-means (roller, hammers, and the like) which press-surfaces of the pressmeans must have substantially the same temperatureof T; (or k.T,,) in order not to cool down the FE wires before the required compremingdeformation of the cross-sections of the wires has been reached. The second operation may be done simultaneously with the first operation. The compressing-deformation action. must be so chosen that the wires when the operation has just been finished (the P, has just been applied) the filtering spaces between the longitudinal wires (mesh=D) are eliminated, which is the caseoperation consisting of cooling; self-cooling at I newly born free-spaces, meshes, between the wires, which free-spaces will then become in their total, measured per one (1) inch, equal to substantially T multiplied by the co-eflicient C of the lineal thermic expansion. This so-acquired very small amount substantially =T C. will form the total sum of the newly born meshes, therefore T C=m.D and the D will then be equal (substantially) to r It may be remarked that the transversal wires being made from a material like Invar, willnot contract when the FE will be cooled down from (T +T to the T temperature. The use of the formula andproviding any desirable accuracy of the smallest dimensions of the filtrating mesh D.

By way of example a practical application will .be shown. FE (having non-square mesh form) consisting of m+1 longitudinal copper wires and (approximately) transversal wires made from Invar. Copper having C=0.000016'7.

First operationheating the FE by T,, centigrade=l00. This heating will increase the linear measure of 1" of a:mD=l00. 0.0000167=0.00167 of an inch. If now this FE is subjected to the second operation, i. e. a pressure of P at the same T centigrade temperature and then the third operation is applied, then such FE will obtain a newly born total of meshes=to the abovementioned mD'=0.00l6'7 per each of one inch, so

that if we have 301 longitudinal wires per inch,

then the total number of meshes formed between two of each longitudinal wires, in one inch length, will be m=300 and we will obtain D ao In the same example if T is only then all the data for D000) D000 etc. will be halved.

In the described third aspect D: we.

of an inch C=% coefiicient of linear thermic expansion The use of this formula provides all answers re the figures to choose. For instance, 'if the security co-efllcient will be chosenS=0.666.and if T= temperature in centigradc -H is prescribed to be 0.00003", then for an example with 200 longitudinal copper wires per inch, we'will have D=0. 00003 -0.66=0.00002 then T will be= I substantially 240, which means that ii we employ 200 wires per inch we should use the temperature T =240 centigrade.

To make a proper. application of the third aspect of this invention, it is necessary that the transversal crossing wire should be made from Invar material or similar, which does not change.

substantially when heated up or cooled down.

Such transversal wires made from Invar or similar maybe pressed on very tightly or aflixed by. adhesion or by welding, etc. in the crossing points to the longitudinal wires. When the transversal wires made from Invar or similar will be cooled down from (T,+T to the T, temperature, then they will not displace the distances between the axis of the horizontal wire, even despite the fact that at the same time each diameter of the horizontal wires (i. e. their cross-section) will contract and will form .the filtrating spaces D. The horizontal wires do also contract in their length but this must be considered as being without importance because when placing the transversal Invar wire according to this process, it is advisable to place them at such a distance, one from the other, that suflicient reserve will be provided for contraction in length of the longitudinal wires.

All these examples are only given by way of illustration and approximately; and do not limit the invention to the widest application of the given formula.

A remark must be made that in practice some difficulties will occur in determining the speed of execution of the second operation as well as to 0.0000056" of an inch, beingthe newly born mesh measured at room temperature T, centigrade. 7/

In the same example if m=200, then Dmm= substantially 0.00000835" of an inch.

' If m'=100; then D 100 =0.00 00167".

If m=50; then D(50)= 0.0000334", and so forth. Certain correction of co-efilcient K will slightly alter these theoretical figures and K will be established only in practice in'accordance to each kind of .metal, form of rollers, speed of pressure application, etc.

expansion C should be different for. 5|. and 52 and in many cases it will be advisable to make this diflerence as large as p le, for instance. o make the transversal wires 52 from Invar material or to weld the longitudinal wires between them with Invar material.

' means of a long wire 1.3.

In Figure 8 the Invar transversal wires 6| are welded on the longitudinal wires 66. They may also be woven through the longitudinal wires if the character of the meshes allow.

-In Figure 9 are shown the welding points 63 which weld together the longitudinal wires 62. The welding may be done by employing Invar material or such soldering metals,the thermic coefllcient of which is extremely small. The'welding may be done without any soldering material. 10

In this case, however, the welding should be done after the meshes have already been formed by means of one of the processes described in this specification.

In Figure 10, the welding is done in curved lines following the dotted lines 65. The longitudinal wires 64 are held together by means of the welding points placed on the crossing of the dotted lines 65 with the longitudinal lines 64.

.On Figures 11,and 12 the filtering element composed of a plurality of longitudinal wires 66 is made rigid by welding on both surfaces of the transversal wires 61 on upper surface and 68 on the lower surface.

On Figure 13 a filtering element composed of a plurality of longitudinal wires 69 is held together by means of welded points 10 and the whole element is solidly attached or fixed on a rigid frame H.

Figures 14 and 15 show the filtering element Figures 18 and 19 show a filtering element formed by a long wire 16 wound around an elliptical core 11.

In Figure 2 is shown a small portion of longitudinal wires 5| as they appear before applying the pressure on their upper and lower surfaces.

In the same figure 53 shows the cross-section of the said wires 5| after the pressure has been applied and the desirable. deformation reached by which the meshes have been formed mechanically, without application of the phenomena of expansion and contraction of materials as described in the third aspect of this invention.

Figure 3 represents the same idea as in Figure 2 using instead of circular cross-sectional, hexagonal cross-sections of the longitudinal wires. 55

In both Figures 2 and 3 the transversal wires or the welding points between the longitudinal wires are not shown.

In Figures 4, 5, 6, and 7 is shown a method of 1 be equal to about /34". In Figure '7 is shown 560 an adjustable edge which could be with the necessary precision, so placed and thereafter rigidly afilxed by suitable means that the desirable predetermined gabarit is obtained. Instead of one, the two edges may be adjustable.

This example shows clearly how the theory of variation as explained in the second aspect of this invention could be applied, especially when it is desirable to obtain very small meshes.

In Figure 6 it is shown how the longitudinal wires 51 in the case of Figure 5 may be placed in respective guideways 58, which may be desirable in the event the meshes are too big and the theory of variation cannot give sufllcient accuracy.

.In Figure 20, plate I8 is made from Invar material. On this plate is placed longitudinal wires 19 having a mesh distance 80 between them and being each of a diameter 6|. The axis of'the longitudinal wires are placed one in relation to another having a distance of 82. If heat and pressure are applied as shown in Figure 21 wherein the filtering element 19 has been compressed together insuch a way that the distance between their axis 82 has remained substantially the same but the meshes between theminstead of remaining equal to 80 as shown in Figure 20 has been practically eliminated; becoming a contact surface 85, which has been obtained by the application of the pressure, provided between the surfaces 83 and 84. 83 and 84 maybe made from Invar material or similar, may be in roller form or hammer, plane or any curvedsurface. By usingthe Invar material for 83 and 84, the variation of the temperature will then not aflect the displaceformation of the meshes, one of the surfaces may be removed and the filtering element could then be rendered rigidby such means as welding, soldering the wires together, etc.

In Figure 22 is shown a filtering element in cross-section wherein the longitudinal wires 81 are soldered on the transversal Invar wires 86.'

Figure 23 shows schematically a roller 88 and a surface 89 between which passes the filtering element 90. v

. In Figure 24 are shown two rollersill and 92 between which passes the filtering element 93. A casing 94 surrounds the rollers and inside of this casing is kept the necessary temperature, or if desired, the casing is filled by vapors which will decrease the cohesional eflect between the wires.

application of the second aspect of this invention 00 wherein on the gabarit plate- 55, which has the same length and dimensions between the gabarit edges-56 and which by example has been chosen equal to two inches.

' In Figure '4 in this predetermined gabarit form 5 between 66a and .6617 are placed seventeen wires,

by way of example, each of which is his" in diameter. These seventeen wires form sixteen meshes each of which isequal to about /15 of an inch.

In Figure 5 when placing only nine wires of he" diameter we obtain 8 meshes each of which is equal to about he".

In Figure '7 whenplacing 22 wires .of he" diameter we obtain 21 meshes each of which will If the wire comes out of the casing through the opening 95, it may if desired, pass through a slightly curved opening formed by guideway- 96 and the roller 91 for purposes of facilitating the opening of the meshes.

A fourth aspect of this invention is the manu; facture of new kinds of FE which consist only of longitudinal wires laid parallel one to another,

and no crosswfres nor transversal wires are prom1 point in a spiral form (substantially circuto place the FE temporarily in a special frame or holder,- made preferably from Invar material. Forinstance, both sides of the FE atthe ends of the longitudinal wires are placed between two plates or two bars of Invar material, so that the FE is practically held in it during the application of the third aspect ofthe invention. After such application the FE is cooled down and the meshes are formed accordingly; then such FE is sub jected to a special weldingor soldering operation consisting of welding together the appropri ated points of the longitudinal wires, and this will replace the absent transversal wires. This welding or soldering may be made electrically or by other means. The welding may follow imaginary transversal lines or points and may be chosen in any direction and having any contour.

They may be done on one side only or on both sides-they may be done in the form of points or short lines or in curves. Such new kind of FE will have a very smooth surface becauseof the.

absence of the transversal crosswires, being more durable because of having no cross points in which the material is-usually deformed abnormally; they will be lighter and substantially thinner and will offer more filtrating efilciency because each mesh D will be more efllcient, and the total of meshes (mD) being much greater per square inch than in ordinary FE.

= Instead of employing frames of Invar material, the FE may be put temporarily between two parallel plates of Invar material, or may be passed through rollers made from Invar material. In this latter case, when the FE, having still the temperature of approximately T f is passed uninterruptedly through cold rollers, cooled down to T, or lower, the pressure between these rollers (made of Invar material) being sufficient to prevent a free displacement of the axis or the I'Es wires in relation one 'to another, displacement which may be caused by the cooling down of the wires; then uninterruptedly the electric welding as described previously will take place. Just before and during the application of the operation of the welding, it is advantageous to coolthe FE 1 as low as economically possible. The fifth aspect of thisinvention consists of an application onvthe' FE of a mechanical pressure without any heat supply (P cold) until the meshes are entirely closed'or nearly closed, and only after this operation to submit such an already compressed or slightly deformed FE to the third operation as described in the third aspect.

The sixth aspect of this invention is the question of the manufacturing of FE wherein the necessary treatment is appliedto eliminate or to reduce to a minimum the cohesional force between thewires of the FE. For this reason it is recommended a previous polishing of wires, dry

or wet-with or without chemicals, or a slight greasi g or "oxidizing of them. It may also be recommended to prosecute the operation of the application of heat (12,) and of the pressure (P,,) in an "atmosphere" of a filled air, of water vapor, or vapor of benzine,- benml, gasoline, toluol, alcohol or the like. The seventh aspect of this invention consists of applying to the=FE a mechanical pressure un-.

der such conditions wherein the cohesion between the crossing points of the woven wires willbe increased. Such operation may be done for example in vacuum casing or with the assistance of special chemicals to de-grease the film of any nature with which the wires of the FE may be I The ninth aspect of this invention is a special I cross-section of wires offering easier control of their deformation when pressure is applied upon, and offering better homogeneity of D. Such cross-sections of the wires may be in either a circular, square, parallelogram or hexagonal form of equal or unequal sides (by groups of 2), or elliptical former a combination of two fiat sides (an opposite pair of sides) with curves above and below. or any other suitable shape. Wires having cross-section with special cutout borders from one of their sides, and other sides provided with a fitted in border can be assembled together one parallel with the other, the

cut-out border 'of the cross-section touches slightly the fitted in border of the same crosssection, and this offers an easy control of D. This is especially important for filtering elements which have no transversally-crossing wires.

The tenth aspect of the invention consists in composing the same FE with at least two different kinds of wires-for instance, the longitudinal wires-being made of one material (one kind of metal or metal alloy) and the transversal wires from any other kind of material so chosen that their respective co-eflicients of thermic expansion (C1 and C2) of these materials will be different. If the difference between C1 and C: will be sufficiently large, then the material from which the transversal wires are made, may substantially replace the use of lnvar or like materials.

The eleventh aspect of this invention consists in submitting the FE to the hardeningor the heat treatment, tempering, annealing or ageing, etc., or any combination of the same after the FE has been produced.

The twelfth aspect of this invention refers to a special electro-welding apparatus for welding the non-crossing FE wherein one part .of it is a knife-like or saw-like device, sufficiently sharp on its side; this knife-like device will contact the be charged by a negative pole of .the current in the case of direct current. The other part of the apparatus may also be a knife-like or saw-like device, or a bar or plate-etc. When FE contain transversal wires, then .these transversal wires when placed insuitable places may be welded or soldered on the surface of the non-crossing FE simultaneously with the longitudinal wires (or wires replacing them in coil-disc form of FE) being welded between them following their crossing points with the transversal wires The thirteenth aspect of this invention consists in appropriate use of the apparatus required for the application of the pressure for this method. This apparatus may be mechanical roller presses This may also be realized by means of of the special aspects of pressing apparatus for this purpose may be so realized that it works by means of a mixed roller-hammer action effected by a movable roller (or rollers) which roller (or rollers) itself provides a hammer-action. Another aspect of a pressure apparatus is an apparatus consisting of at least two pressing-edged surfaces having their press-edges in the form of a strip or bar, which. edges compress between them thepas'sing FE, which compression is realized by means of vibratory-hammering of one or both of these edges.

The heating apparatus may be fitted closely to the working surfaces of the press-apparatus, and if necessary, the complete machinery-(heat supplying apparatus and the transporter of FE and the mechanical press, etc.) may all be placed in a casing, wherein the required temperature' (T +T will be maintained.

The fourteenth aspect of this invention consists of making the FE not from metal but from other suitable solids such as for instance, glass,

celluloid, condensation products, plastic materials and the like-then if welding cannot be applied it may be replaced by sticking processes or equivalent chemical reactions, combining the wires between them.

Various changes may also be made of the completed FE and in the embodiments of the metals we desire without departure from the spirit and rality of transverse wires having a relatively low coefiicient of expansion transverse to the first mentioned wires and in contact therewith in a plane parallel to the plane of the first mentioned wires, welding the transverse wires to the first mentioned wires while at substantially the said temperature, the coefllcient of expansion of the transverse wires being so low that theirdecrease in length when cooled does not substantially decrease the distance between the first mentioned wires.

2. The method of manufacturing a filter element which comprises placing a plurality of metallic wires having a coefllcient of linear. expansion of at least 0.00001 per 1 C. and a diameter of at least 0.01 mm.'in a common plane and in parallel relation with each of said wires in contact with an adjacent wire throughout substantially its entire length, heating said wires to a temperature of at least 50 C., placing a plurality of transverse wires having a relatively low coefficient of expansion transverse to the first mentioned wires and in contact therewith in a plane parallel to the plane of the first mentioned wires, welding the transverse wires to the first mentioned wires while at substantially the said temperature, the coefiicient of expansion of the transverse wires being so low that their decrease in length when cooled does not substantially decrease the distancebetween the first mentioned wires, said first mentioned wires being previously of any kind, or hammer-presses of any kind; Onev subjected'to a process diminishing the cohesion between their respective adjacent surfaces.

3; The method of manufacturing .a filter element which comprises placing a plurality of glass wires having a coefficient of linear expansion of at least 0.000007 per 1 C. and a diameter of at least 0.1 mm. in a common plane and in parallel relation with each of said wires in contact with an adjacent wire throughout substantially its entire length, heating said 'wires to a temperature of at least 50 C., placing a plurality of transverse wires having a relatively low coefilcient of expansion transverse to the first mentioned wires and in contact therewithin a plane parallel to the plane of the first mentioned wires, welding the transverse wires to thefirst mentioned wires while at. substantially thesaid temperature, the coefiicient of expansion of the transverse wires being so low that their decrease in length when cooled does not substantially decrease the distance between the first mentioned wires.

4. The method of manufacturing a filter element which comprises placing a plurality of metallic wires having a coefiicient of linear expan: sion of 0.00001 per 1 centigrade and a diameter of at least 0.01 mm. in a common plane, said wires being at a distance apart of their adjacent wires of at least 0.001 mm. and in parallel relation with each of said wires, applying pressure to said first mentioned wires to deform same up to the moment that each of the said first mentioned wires comes in contact with an adjacent first mentioned wire substantially'throughout its en tire length, heating said wires to atemperature of at least 5 0 0., placing a plurality of transverse wires having a relatively low coeflicient or expansion transverse to the first mentioned wires and in contact therewith in a plane parallel to the plane of the first mentioned wires, welding the transverse wires to the first mentioned wires while at substantially the said temperature, the coefiicient of expansion orthe transverse wires being so low that their decrease in length when cooled does not substantially decrease the distance between the first mentioned wires.

5. The method of manufacturing a-filter element which comprises winding of at least one metallic wire having a coefiicient of linear expension of at least 0.00001 per 1 centigrade and a diameter 'of at least 0.01 mm. in a common plane and in such relation that each winding of the said first mentioned wires contacts, with an adjacent winding of the said first mentioned wires through substantially its entire length,

heating said wire to a temperature or at least 50 C., placing a plurality 0t transverse wires having a relatively .low coefiicient of expansion transverse to the said windings oi the said first mentioned wires and in contact therewith in a plane parallel to the plane of the said firstimem. tioned wires, welding the said transverse wires to the said first mentioned wires while at substantially thesaid temperature, the coefllcient of expansion of the said transverse wires being so 65.

" does not substantially "decrease the distance between the said first mentioned wires.

low that their decrease in length when cooled apart from their adjacent ones of at least 0,001 mm., applying pressure to the first mentioned wires to deform same up to the moment that each of said first mentioned wires comes in contact with an adjacent first mentioned wire substantially throughout its entire length, heating to the said windings of the said first mentioned 10 wires and in contact therewith in a plane parallel to the plane of the said first mentioned wires, welding the said transverse wires to the said first mentioned wires while at'substantially the said temperature, the coeflicient of expansion of the said transverse wires being so low that their decrease in length when cooled does not substantially decrease the distance between the said first mentioned wires.v

GECQGE ALEXIS RUBISSOW. 

